This invention relates generally to a push rod stroke length gage for use on the air brake systems of semi-trailer trucks.
Most air brake systems utilize a sealed housing, within which is a diaphragm attached to a push rod that extends from one side of the housing. The opposite side of the diaphragm creates an air cavity within the housing. The air pressure in the cavity rises when the brake pedal of the truck is depressed. The diaphragm deforms, and the air pressure rises, in proportion to the amount of force applied to the brake pedal. The push rod responds by moving with the diaphragm to engage the braking surfaces. When the air brake system is properly adjusted, the push rod will travel a distance on the order of one to two inches from the point where the brake is completely released to the point where it is fully actuated. Over time, as the brakes are repeatedly applied, the push rod travel distance increases, eventually requiring a readjustment of the brake system before the braking capability deteriorates to a level that renders the truck unsafe.
The brake systems of most trucks are normally examined on the basis of elapsed mileage since the last adjustment. Because the rate at which brake systems wear and fall out of adjustment varies between trucks, many trucks' brake systems have already deteriorated beyond what is considered safe when the brakes are examined, while other trucks' braking systems are still within tolerance and require no readjustment after the same elapsed mileage. Both of these unwanted situations should be avoided. An improvement that would allow the brakes to be quickly checked is desired in order to prevent potentially unsafe conditions from developing prematurely and to avoid wasting money for unnecessary down time. It is also desirable that such an improvement be inexpensive and easily adaptable to existing air brake systems.
The present invention answers the need for a simple device that can be used to quickly ascertain whether an air brake system is adjusted to Department of Transportation standards, at any time at any location and without the need for a mechanic or extraneous tools. The present invention is also inexpensive and easily adaptable to most air brake systems.